Steppers mis-step if the acceleration and/or speed is too high for the load.
Without your code not much else can be said. As usual post your code, all
of it, in a state that compiles, in code-tags please.
Please also post links to datasheets for all the hardware (motor, controller)
since we need to see these too.
You mention the width of the step pulses - this is not important, the step
pulse just has to be 10us or more, the step happens on the rising edge
with most controllers. What matters is that the direction signal is setup
before the step pulse, and that the step pulse timings don't exceed the
maximum speed or acceleration abilities of the motor with its load (both
found be experiment, typically).